1. Field of the Invention
This invention relates to a linear motion rolling guide unit providing guide operation by rolling rollers on four raceway faces formed in a track-rail having raceway face.
2. Description of the Related Art
One of the conventional linear motion rolling units of the type described above is illustrated in FIGS. 13 to 19. The conventional unit has a pair of raceway faces formed on each side face of a track-rail R, that is, the lower raceway faces 1a, 2a and the upper raceway faces 1b, 2b. The lower and upper raceway faces 1a and 1b, 2a and 2b, are positioned forming an approximate right angle with each other. A recessed portion 3 is formed between the lower raceway face 1a and the upper raceway face 1b. Likewise, a recessed portion 4 is formed between the lower raceway face 2a and the upper raceway face 2b. 
A slider S runs on the track rail R having such raceway faces. The slider S includes end caps 5 and 6 respectively combined with the front and back ends of a casing c. The casing c and the end caps 5 and 6 straddle the track-rail R having the raceway faces, to move along the track-rail R. The slider S is bilaterally symmetrical with respect to the axis the track-rail R having the raceway faces. Therefore, the structural elements in bilateral symmetry will be hereinafter described by use of the same reference numerals or symbols. The description is given relating only to the raceway faces 1a and 1b as a representative example.
A pair of guide holes 7 and 8 is located in the casing c to extend flush with and parallel to the raceway faces 1a and 1b (and to the raceway faces 2a and 2b) formed on the track-rail R. The guide holes 7 and 8 extend through the casing c in the axis direction and are parallel to each other in upper and lower positions. Guide cylinders 9 and 10 shown in FIG. 14 are respectively inserted into the guide holes 7 and 8.
Each of the guide cylinders 9 and 10 is made up by combining two semicircular cylinder members together. Rollers 11 and 12 roll in the respective guide cylinders 9 and 10 in a such manner as to be parallel to the respective raceway faces 1a and 1b (to the respective raceway faces 2a and 2b). As can be seen from FIG. 13, the rollers 11, after rolling in the guide cylinder 9 of the upper guide hole 7, are guided in a direction that brings them into contact with the lower raceway face 1a (2a), while the rollers 12, after rolling in the guide cylinder 10 of the lower guide hole 8, are guided in a direction that brings them into contact with the upper raceway face 1b (2b). In this manner, the rollers 11 and 12 individually alternate between the upper and lower positions during their rolling movement, and the turning points are provided in the end caps 5 and 6.
As shown in FIG. 15, a pair of intersecting passage grooves 13 and 14 is provided in each of the end caps 5 and 6. The passage groove 13 is deeper than the passage groove 14, as shown in FIG. 16. The passage groove 13 would obstruct the continuity of the passage groove 14. To avoid this, a bridge member 15 as illustrated in FIG. 16 is installed across the location where the continuity is obstructed. The bridge member 15 has a U-shaped end face. As can be seen from FIG. 16, the bottom 15a is formed in an arc shape continuous with the groove portions 14a and 14b of the passage groove 14. The U-shaped bridge member 15 rests on bridge steps 16 which are provided parallel to the passage groove 13. FIG. 17 illustrates the bridge member 15 on the bridge steps 16.
FIG. 17 illustrates the end cap 5. By mounting the bridge member 15 in this manner, the groove portion 14a, the bottom 15a and the groove portion 14b are connected continuously to each other to form the passage groove 14. By mounting the bridge member 15 as shown in FIG. 17, the passage grooves 13 and 14 are defined by the bridge member 15 and intersect with each other in a multilevel manner in a position corresponding to the bridge member 15. FIG. 17 further shows a cap member 17 which is mounted in a direction at right angles to the passage groove 14 and has two ends resting on supporting steps 18 as shown in FIG. 16.
Two pairs of convexities 19 and 20 are provided on the respective ends of the passage grooves 13 and 14 which are father away from the track-rail R having the raceway faces, as shown in FIG. 15. A fitting recess 21 is formed between the pair of convexities 19, and a fitting recess 22 is formed between the pair of convexities 20. Two pairs of convexities 23 and 24 are provided one step higher up than the respective pairs of convexities 19 and 20. The outer peripheries of the convexities 19 and 23 are combined together to form an arc shape in alignment with the outer periphery of the guide cylinder 9, and likewise the outer peripheries of the convexities 20 and 24 are combined together to form an arc shape in alignment with the outer periphery of the guide cylinder 10.
As is clear from FIG. 14, projections 9a and 10a are provided at ends of the guide cylinders 9 and 10, and designed to be tightly fitted into the respective fitting recesses 21 and 22. By tightly fitting the projections 9a and 10a into the fitting recesses 21 and 22, each of the guide cylinders 9 and 10 which are each made up of two members is kept in one piece. The ends of the guide cylinders 9 and 10 with the projections 9a and 10a fitted into the fitting recesses 21 and 22 are in contact with the convexities 19, 20 and the convexities 23, 24, so that the continuity between the guide cylinders 9 and 10 and the respective passage grooves 13 and 14 is maintained.
Accordingly, the rollers 11 and 12, which have been respectively guided from the guide cylinders 9 and 10 to the passage grooves 13 and 14, are further guided from access portions 25 and 26 which are the other ends of the passage grooves 13 and 14, onto the lower raceway face 1a and the upper raceway face 1b of the track-rail R having the raceway faces. Alternatively, the rollers 11 and 12, which have reached the end cap 5 or 6 from the lower raceway face 1a and the upper raceway face 1b, are then guided from the access portions 25 and 26 into the passage grooves 13 and 14. Note that FIG. 19 is a sectional view of the slider S straddling the track-rail R having the raceway faces. FIG. 13 also shows a retaining plate 29 provided for preventing the rollers 11 and 12 guided from the access portions 25 and 26 as described above from falling out of the slider S.
FIG. 14 also shows underside sealing members 27 that are provided for sealing the underside of the slider S for preventing the intrusion of dust and the like from the underside to the slider. In addition, end seal members 28 are provided on the outer sides of the respective end caps 5 and 6 for preventing the intrusion of dust and the like from the directions of movement of the slider.
Upon the movement of the slider S along the track-rail R having the raceway faces, the rollers 11 and 12 installed in the slider S roll along move on the raceway faces 1a and 1b (and 2a and 2b) to ensure a smooth movement of the slider S. The following is the moving path of the rollers 11 and 12.
In accordance with the moving direction of the slider S, for example, the rollers 11 and 12 are introduced from the access portions 25 and 26 shown in FIG. 15 into the passage grooves 13 and 14 or onto the raceway faces 1a and 1b (also 2a and 2b). First, the case of the rollers 11 and 12 introduced from the access portions 25 and 26 into the passage grooves 13 and 14.
Let us assume the slider S is moved and the rollers 11 are introduced from the access portion 25 and the rollers 12 are introduced from the access portion 26 of the end cap 5 or 6 which is located to the rear of the moving direction of the slider S. The rollers 11, after entering the access portion 25, are guided into the passage groove 13 and then into the guide cylinder 9 that is connected to the end of the passage groove 13 opposite to the access portion 25. Similarly, the rollers 12, after entering the access portion 26, are guided into the passage groove 14 and then into the guide cylinder 10 that is connected to the end of the passage groove 14 opposite to the access portion 26. At this point, the row of rolling rollers 11 and the row of rolling rollers 12 intersect with each other on either side of the bridge member 15, as can be seen from FIG. 17. This intersection of rows of the rolling rollers is represented by the rollers 11 and 12 in FIG. 14.
The rollers 11 and 12 after having intersected with each other in one end cap 5 or 6 in this manner are guided from the passage grooves 13 and 14 through the guide cylinders 9 and 10 into the other end cap 6 or 5 that is located to the front of the moving direction of the slider S. Then, in the end cap 6 or 5 located to the front of the moving direction, the rollers 11 and 12 are introduced into the ends of the passage grooves 13 and 14 opposite to the access portions 25 and 26. Then, the rows of rolling rollers 11 and 12 intersect with each other while moving through the passage grooves 13 and 14.
Such a conventional linear motion rolling guide unit as described above needs a large number of parts incorporated in the end caps 5 and 6, and in addition the guide cylinders 9 and 10 are independent of these incorporated parts. In consequence, the problem of a significantly low efficiency of the assembly process for the entire unit arises. It is needless to say that another problem is the increase in the manufacturing cost for the parts because of the large number of parts.
Further, when the number of parts incorporated in the end caps is large, the dimensional tolerance and the like of the parts affects the junction between the parts, and inevitably a gap and/or a difference in level easily occur at such a junction. Once the gap and/or the difference in level occur, they cause the rollers 11, 12 to tilt or to catch, or alternatively cause the abrasion of the guide cylinders 9, 10. As a result, the smooth circulation of the rollers 11 and 12 is impeded. A problem rising for this reason is variation in the frictional resistances of the slider S to the track-rail R when the slider S runs on the track-rail R having the raceway faces.